The present invention relates to internal combustion engines; more particularly, to devices for controlling systems in an internal combustion engine; and most particularly, to an improved hydraulic manifold assembly for controlling the flow of engine oil in variable activation and deactivation of valve lifters in an internal combustion engine.
In conventional prior art four-stroke internal combustion engines, the mutual angular relationships of the crankshaft, camshaft, and valves are mechanically fixed; that is, the valves are opened and closed fully and identically with every two revolutions of the crankshaft, fuel/air mixture is drawn into each cylinder in a predetermined sequence, ignited by the sparking plug, and the burned residue discharged. This sequence occurs irrespective of the rotational speed of the engine or the load being placed on the engine at any given time.
It is known that for much of the operating life of a multiple-cylinder engine, the load might be met by a functionally smaller engine having fewer firing cylinders, and that at low-demand times fuel efficiency could be improved if one or more cylinders of a larger engine could be withdrawn from firing service. It is known in the art to accomplish this by de-activating the valve train leading to preselected cylinders in any of various ways, such as by providing special valve lifters having internal locks which may be switched on and off either electrically or hydraulically. Such switching is conveniently performed via a hydraulic manifold that utilizes electric solenoid valves to selectively pass engine oil to the lifters upon command from an engine control module (ECM). Such a manifold is referred to in the art as a Lifter Oil Manifold Assembly (LOMA).
It is a principal object of the present invention to provide an improved solenoid-actuated hydraulic manifold assembly for controlling the hydraulic locking and unlocking of deactivatable valve lifters in an internal combustion engine, wherein at least a portion, and preferably all, of the manifold components are formed by injection molding of a polymer.
It is a further object of the invention to provide such a manifold assembly wherein any trapped air is automatically purged immediately upon engine startup and is prevented from re-entry during engine operation.
It is a still further object of the invention to provide such an assembly comprising a minimum number of components which then may be easily fabricated, and preferably which are formed of a suitable thermoplastic polymer such that the components may be fusibly joined without threaded fasteners as by vibration welding.
Briefly described, a hydraulic manifold assembly for variable actuation of engine valves in accordance with the invention includes first (top) and second (bottom) plates having portions of oil flow passages, or galleries, integrally molded therein. The plates are formed preferably by injection molding of a suitable high temperature thermoplastic polymer. The plates are joined together as by cementing or preferably by fusion welding (vibration welding) along mating surfaces, obviating the need for separate fasteners and for internal seals on the flow passages. The assembly further comprises a retainer for retaining a plurality of individual solenoid-actuated valves in operational disposition in sockets formed in the plates. Preferably, the retainer is formed with air passageways so as to function simultaneously as a positive crankcase ventilation (PCV) baffle that attaches to the plates via integrally molded releasable snap clips. The present hydraulic manifold results in a weight savings and a substantial savings in manufacturing cost over prior art manifolds formed of cast aluminum.